1. Field of the Invention
This invention relates to control means for optical instruments and has particular reference to apparatus for automatically adjusting amount of axial change required in an astigmatic refraction finding.
2. Discussion of the Prior Art
Traditionally in refracting eyes, refinement of the axis of the corrective cylinder power is accomplished by using a cross cylinder lens which has a fixed axial relationship to the corrective cylinder power. This cross cylinder lens is flipped about an axis to determine the best visual clarity. The operator interprets the response of the patient by arbitrarily increasing or decreasing the axis of the corrective cylinder power a fixed amount or an amount intuitively interpreted based on the corrected cylinder power and experience.
The present invention avoids reliance upon the operator for determination of amount for which axis of the correcting cylinder lens is changed and, accordingly, there is the object of automatically effecting the change of cylinder axis required for patient correction based upon the amount of corrective cylinder power in the viewing path.
More particularly, there is the aforesaid object of obviating reliance upon operator experience and intuitiveness in adjusting axis of corrective cylinder power.
Other objects and advantages of the invention will become apparent from the following description.